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Transmissivity (τ) is the fraction of incident radiation flux transmitted through a body or material. It represents the portion of radiation that passes through without being absorbed or reflected.
The calculator uses the fundamental radiation balance equation:
Where:
Explanation: This equation is based on the conservation of energy principle, where the sum of transmitted, absorbed, and reflected radiation must equal the total incident radiation (normalized to 1).
Details: Calculating transmissivity is crucial in various fields including optics, thermal engineering, solar energy systems, and material science. It helps determine how much radiation passes through materials like glass, filters, and atmospheric layers.
Tips: Enter absorptivity and reflectivity values between 0 and 1. Ensure that the sum of absorptivity and reflectivity does not exceed 1, as this would violate energy conservation principles.
Q1: What are typical values for transmissivity?
A: Transmissivity values range from 0 (completely opaque) to 1 (completely transparent). Common materials like window glass have τ ≈ 0.85-0.90.
Q2: Can transmissivity be negative?
A: No, transmissivity cannot be negative as it represents a fraction of transmitted radiation. Values must be between 0 and 1.
Q3: What if absorptivity + reflectivity > 1?
A: This violates energy conservation. The sum of α + ρ cannot exceed 1, as this would imply more energy is absorbed and reflected than is incident.
Q4: How is transmissivity measured experimentally?
A: Typically measured using spectrophotometers or radiometers that compare incident and transmitted radiation intensities.
Q5: Does transmissivity depend on wavelength?
A: Yes, most materials have wavelength-dependent transmissivity. This calculator provides the spectral average unless specified otherwise.